Hand-held power tool

ABSTRACT

A hand-held power tool for driving a grinding and cutting working tool ( 12 ) which is mounted on a drive spindle ( 13 ) projecting from the power tool housing ( 11 ), includes a locking and holding device ( 20 ) for releasably securing a protective hood ( 17 ), which at least partially covers the working tool ( 12 ) on the housing ( 11 ), with the holding device ( 20 ) having a clamping stirrup ( 22 ) for securing the protective hood ( 17 ), and a tensioning lever mechanism ( 21 ) with a tensioning lever ( 23 ) displaceable between a first position in which the clamping stirrup ( 22 ) is released and has a first stirrup width, and a second position in which the clamping stirrup is tensioned and has a second stirrup width smaller than the first stirrup width, and a locking spring ( 24 ) radially displaceable by the tensioning lever ( 23 ) and having at least one locking nose ( 25 ) for retaining the protective hood ( 17 ) on the housing ( 11 ) without a possibility of rotation relative thereto in the second position of the tensioning lever ( 23 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hand-held power tool for driving cutting or grinding working tools.

2. Description of the Prior Art

Hand-held power tools of the type described above such as, e.g., angle grinder, have a circular disc-shaped cutting or grinding working tool rotatable during operation and used, e.g., for forming cuts in constructional components or for grinding surfaces of constructional components. The cutting or grinding working tool is covered circumferentially at least partially with a protective hood.

German Publication DE 39 21 772 A1 discloses a hand-held power tool which is formed as an angle grinder and includes a protective hood releasably mounted on the power tool housing. To this end, the housing, in the region of the drive spindle exit, has a locking and holding device for securing the protective hood on the housing. An annular clamping stirrup of the locking and holding device and the diameter of which is adjusted by a tensioning lever, is fixedly secured on the housing. The clamping stirrup is arranged about the spindle and receives an annular flange of the protective hood which is forcelockingly and frictionally secured in the clamping stirrup. However, the protective hood is not formlockingly secured against rotation.

German Publication DE 102 59 520 A1 discloses a hand-held power tool for a rotational disc-shaped working tool having a housing from which a drive spindle projects for mounting a working tool thereon and on which a hollow cylindrical locking neck, coaxial with the drive spindle, is formed. A protective hood for at least partially covering the working tool is releasably mounted on the housing. The protective hood is mounted on the locking neck and is secured thereon by a clamping stirrup provided with locking screws. For mounting the protective hood in a desired rotational position relative to the housing, without using any auxiliary tool and for securing the protective hood in that position, the clamping stirrup is pivotally mounted on the locking neck and is retained there with manually releasable locking means arranged between the locking neck and the clamping stirrup and independent of the locking screws. The drawback here consists in that several expensive operational steps are necessary for mounting the protective hood and fixedly securing it against rotation.

An object of the present invention is to provide a hand-held power tool in which the drawbacks of known hand-held power tools are eliminated, and the protective hood is securable on the housing against rotation relative thereto in a constructively simple way.

SUMMARY OF THE INVENTION

This and other objects of the present invention, which will become apparent hereinafter are achieved by providing a hand-held power tool for driving a cutting or grinding working tool and including a housing, a drive spindle extending from the housing for mounting the working tool thereon, a protective hood for at least partially covering the working tool and securable on the housing, and a locking and holding device for releasably securing the protective hood on the housing and having a clamping stirrup for securing the protective hood and having a variable stirrup width, and a tensioning lever mechanism having a tensioning lever for operating the clamping stirrup and displaceable between a first position in which the clamping stirrup is released and has a first stirrup width, and a second position in which the clamping stirrup is tensioned and has a second stirrup width smaller than the first stirrup width, and a locking spring radially displaceable by the tensioning lever and having at least one locking nose for retaining the protective hood on the housing without a possibility of rotation relative thereto in the second position of the tensioning lever.

The present invention insures fixing of the protective hood on the housing and securing of the mounted protective hood against rotation relative to the housing without any auxiliary tool or tools in a single operational step, with the locking and holding device requiring only one additional component for forming the locking mechanism. Here, “against rotation,” means not only that no pivotal movement relative to the housing becomes possible but rather that any rotation relative to the housing (about the drive spindle axis) is prevented.

Advantageously, the clamping stirrup and the tensioning lever mechanism are fixedly secured on the housing and the protective hood has counter-locking means engageable, in the second position of the tensioning lever, by the at least one nose of the locking spring for retaining the protective hood on the housing without a possibility of rotation relative thereto.

As a result, there is no need to provide separate counter-locking means on the housing and, in particular on the housing flange of the hand-held power tool, which are expensive to produce and install. Besides, the working and protective region is not limited in any way as the protective hood is rotatable by 360°. Because the protective hood has no interfering operational handle, a further advantage consists in that in each position, a maximal cut depth is available.

It is advantageous when the tensioning lever mechanism includes a tensioning member connectable with the locking spring (a toggle lever design), with the locking spring being arranged on the tensioning member. With such a design, the locking spring can be mounted on the tensioning member in a technically simple manner, by simply being pushed on the tensioning member. Because the tensioning member is displaced radially when the tensioning lever is displaced from its first position (release position of the clamping stirrup) to its second position (tensioning position of the clamping stirrup) and vice versa, the tensioning member is particular suitable as a carrier of the locking nose of the locking spring.

It is also advantageous when the locking spring is formed as a leaf spring, so that the transition of the tensioning lever mechanism from a release position of the clamping stirrup into tensioning position of the clamping stirrup is also possible when the locking nose is not engageable with the counter-locking means of the protective hood. The engagement can be effected, e.g., later by rotating the protective hood relative to the housing, so that the locking nose automatically is displaced in its locking position by the biasing force of the leaf spring.

Advantageously, the tensioning member is formed integrally with the leaf spring. Thereby, a particularly convenient manufacturing of the assembly becomes possible. Thus, the tensioning member can be, e.g., economically formed as a stamped and bent part.

According to an alternative embodiment of the present invention, the locking spring is formed as an elongate spring clip having two opposite end sides in a longitudinal direction of the spring clip and each having an opening through which the tensioning element is extendable. Thus, during mounting of the locking and holding device, the tensioning member should be passed through both openings in the end sides of the spring clip and then be mounted on the clamping stirrup and the tensioning lever. This makes the mounting of the locking spring very easy and quick.

Advantageously, the counter-locking means of the protective hood is formed as locking teeth which together form mounting means for mounting the protective hood on a housing flange. This design with several locking teeth makes a better clamping possible because the locking teeth are noticeably flexible and as a continuous rim with corresponding tolerances, can be better aligned.

Advantageously, the counter-locking means has a plurality of counter-locking elements uniformly distributed on the protective hood. Therefore, the protective hood can be fixedly secured relative to the housing in a plurality of rotational position.

The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show:

FIG. 1 a side view of a hand-held power tool according to the present invention with a locking and holding device for the protective hood of the power tool in a release position;

FIG. 2 a perspective view of the protective hood and a section of the housing of the power tool shown in FIG. 1;

FIG. 3 a cross-sectional view of a detail of the power tool designated with a Roman numeral III in FIG. 1;

FIG. 4 a partially cross-sectional side view of the power tool shown in FIG. 1 with the locking and holding device for the protective hood in the locking position;

FIG. 5 a cross-sectional view of a detail of the power tool designated with a Roman numeral V in FIG. 4;

FIG. 6 a partially cross-sectional side view of another embodiment of a hand-held power tool according to the present invention with the locking and holding device for the protective hood of the power tool in a release position;

FIG. 7 a cross-sectional view of a detail of the power tool designated with a Roman numeral VII in FIG. 6; and

FIG. 8 a cross-sectional view of the detail VII, as shown in FIG. 7, in a locking position of the locking and holding device.

In the drawings, the same parts are designated with the same reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A hand-held power tool 10, a first embodiment of which is shown in FIGS. 1 through 5, is formed as an angle grinder. As shown in FIGS. 1 and 4, a disc-shaped cutting or grinding working tool 12, which is shown in FIGS. 1 and 4 only schematically, is mounted on the power tool 10 and is driven by a drive unit located in a power tool housing 11. The cutting or grinding tool 12 is secured on a drive spindle 13 projecting from the housing 11 at a housing flange 16. For the cutting or grinding tool 12, a protective hood 17 is arranged on the housing 11. The protective hood 17 is mounted on the housing flange 16 with mounting means 18 (see, in particular FIG. 2) and cover at least partially the cutting or grinding tool 12. For securing the protective hood 17 on the flange 16, there is provided a locking and holding device 20 fixedly connectable with the housing 11 by fastening element 30 in form of screws. The mounting means 18 is formed as an annular member having a plurality of counter-locking elements 19 in form of locking teeth. The locking and holding device 20 has a clamping stirrup 22 having a first end 27, a second end 28, and a tensioning lever-mechanism 21 located between the two ends 27 and 28.

The tensioning lever mechanism 28 includes a tensioning lever 23 pivotally supported by a first pivot support 31 at the stirrup first end 27. A bar-shaped tensioning member 26, on which the tensioning lever 23 is pivotally supported, is itself pivotally supported by a second pivot support 32 and is pivotally secured, at its end remote from the tensioning lever 23, to an abutment 33 at the second stirrup end 28.

A locking spring 24, which is formed as a spring clip, is arranged on the tensioning member 26. The locking spring 24 is shaped as elongate rectangular member extending in the direction of a longitudinal extent of the tensioning member 26 and open at one of its longitudinal sides. On the open longitudinal side, which forms a leaf spring, there are provided, on the locking spring 24, two locking noses 25 located adjacent to the housing flange 16 (see in particular FIGS. 3 and 4). The opposite end sides of the locking spring 24, in the longitudinal direction of the locking spring 24, each has a through-opening 36 (see in particular FIG. 2) through which the bar-shaped tensioning member 26 extends to thereby retain the locking spring 34 on the tensioning member 26.

In FIGS. 1 and 3, the tensioning lever 23 is shown in its first position, with its free end pivoted away from the clamping stirrup 22, in which the clamping stirrup 22 has a first stirrup width (or first diameter) and is released. As particularly shown in FIG. 3, none of the locking noses 25 is located in a gap between the counter-locking elements 19 which are provided on the protective hood 17. In this position of the tensioning lever 23, the protective hood 17 can be taken off of the housing flange 16.

In FIGS. 4 and 5, the tensioning lever 23 is shown in its second position in which its free end engages the clamping stirrup 22. In this position of the tensioning lever 23, the clamping stirrup 22 has a second stirrup width (or second diameter) that is smaller than the first stirrup width (diameter). The clamping stirrup 22 is tensioned. As particularly shown in FIG. 5, at least one of the locking noses 25 is located in the gap between the counter-locking elements 19 which are provided on the protective hood 17. In the second position of the tensioning lever 23, the protective hood 17 is secured by the clamping stirrup 22, which is fixedly mounted on the housing 11, on the housing flange 16. Simultaneously, the locking nose(s) 25 and the counter-locking elements 19 lock the protective hood 17 on the housing flange 16, preventing rotation of the protective hood 17 relative to the housing 11.

FIGS. 6 through 8 show another embodiment of an inventive hand-held power tool 10 that distinguishes from that shown in FIGS. 1 through 5 by the design of the tensioning member 26 and the locking spring 24. Therefore, for the complete description of elements not mentioned below and their functions, reference is made to the description of the embodiment shown in FIGS. 1 through 5. The locking spring 24 is formed integrally with the tensioning member 26. The tensioning member 26 forms two, extending parallel to each other arcuate arms that project from an end side 34, and the leaf spring-shaped spring 24 that has one of its ends connected with the end side 34. The locking nose 25 is provided on an arcuate end of the locking spring 34. The tensioning member 26 is pivotally connected with the abutment 33 on the second stirrup end 28 by a connection element 37 that is formed as a screw, thereby being pivotally supported on the abutment 33. The tensioning member 26 is further pivotally supported on the second pivot support 32 on the tensioning lever 23 with its end remote from the connection element 37.

In FIGS. 6 and 7, the tensioning lever 23 is shown in its first position, with its free end being pivoted away from the clamping stirrup 22, in which the clamping stirrup 22 has a first stirrup width (or a first diameter) and is released. As particularly shown in FIG. 7, the locking nose 25 is not located in the gap between the counter-locking elements 19 which are provided on the protective hood 17. The locking nose 25 is displaced radially outwardly. In the first position, of the tensioning lever 24, the protective hood 17 can be taken off of the housing flange 16.

FIG. 8 shows the tensioning lever 23 in its second position in which the free end of the tensioning lever 23 engages the clamping stirrup 22 and in which, the clamping stirrup 22 has a second stirrup width (or diameter) that is smaller than the first stirrup width (diameter). In the second position of the tensioning lever 23, the clamping stirrup 22 is tensioned. As further shown in FIG. 8, the locking nose 25 extends into the gap between the counter-locking elements 19 provided on the protective hood 17. In the second position of the tensioning lever 23, the protective hood 17 is secured by the clamping stirrup 22, which is fixedly mounted on the housing 11, on the housing flange 16. Simultaneously, the locking nose(s) 25 and the counter-locking elements 19 lock the protective hood 17 on the housing flange 16, preventing rotation of the protective hood 17 relative to the housing 11.

Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is, therefore, not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims. 

1. A hand-held power tool for driving a cutting or grinding working tool (12), comprising a housing (11); a drive spindle (13) extending from the housing (11) for mounting the working tool (12) thereon; a protective hood (17) for at least partially covering the working tool (12) and securable on the housing (11); and a locking and holding device (20) for releasably securing the protective hood (17) on the housing and including a clamping stirrup (22) for securing the protective hood (17) and having a variable stirrup width, and a tensioning lever mechanism (21) having a tensioning lever (23) for operating the clamping stirrup (22) and displaceable between a first position in which the clamping stirrup (22) is released and has a first stirrup width, and a second position in which the clamping stirrup is tensioned and has a second stirrup width smaller than the first stirrup width, and a locking spring (24) radially displaceable by the tensioning lever (23) and having at least one locking hose (25) for retaining the protective hood (17) on the housing (11) without a possibility of rotation relative thereto in the second position of the tensioning lever (23).
 2. A hand-held power tool according to claim 1, wherein the clamping stirrup (22) and the tensioning lever mechanism (21) are fixedly secured on the housing (11), and wherein the protective hood (17) has counter-locking means (19) engageable, in the second position of the tensioning lever (23), by the at least one nose (25) of the locking spring (24) for retaining the protective hood (17) on the housing (11) without a possibility of rotation relative thereto.
 3. A hand-held power tool according to claim 1, wherein the tensioning lever mechanism (21) comprises a tensioning member (26) on which the locking lever (23) is arranged.
 4. A hand-held power tool according to claim 1, wherein the locking spring (23) is formed as a leaf spring.
 5. A hand-held power tool according to claim 3, wherein the locking spring (23) is formed integrally with the tensioning member (26).
 6. A hand-held power tool according to claim 3, wherein the locking spring (23) is formed as an elongate spring clip having two opposite end sides in a longitudinal direction of the spring clip and each having an opening (36) through which the tensioning element (26) is extendable.
 7. A hand-held power tool according to claim 2, wherein the counter-locking means (19) of the protective hood (17) is formed as locking teeth which together form mounting means (18) for mounting the protective hood (17) on a housing flange (16).
 8. A hand-held power tool according to claim 2, wherein the counter-locking means (19) comprises a plurality of counter-locking elements uniformly distributed on the protective hood (17). 